1. Field of the Invention
The present invention relates to control electronics for phased array antenna systems, and particularly to a programmable wide-band radio frequency feed network adapted for a phased array antenna system that uses multiple antenna elements or multiple RF paths to optimize signal transmission and reception.
2. Description of the Related Art
Antenna arrays rely on microwave or radio frequency (RF) feed networks to provide the appropriate excitations for the array to function according to its design specifications. The excitations of the various elements of the antenna array are provided to steer the beam in a certain direction to enhance the communication link (thus beam steering) or create nulls in the radiation pattern of the array to eliminate interference (thus null steering).
There are two degrees of freedom that are usually utilized in the design of microwave feed networks, the amplitude and the phase. The different paths within the feed network are given certain amplitude and phase excitations relative to the center path or one of the edge paths. In most applications, the feed network is fixed and engraved within the hardware of the system or antenna structure, operating at a certain narrow frequency band. Thus, it is optimized to work for that application only and cannot be altered once the design is taped out (fabricated). In other designs, the feed network for that application has one degree of freedom (such as the phase excitations, e.g., those in smart antenna systems with phased arrays, or amplitude excitations). Although the most common design is the one that uses phase changes as the degree of freedom in phased array implementations (because it is convenient to control the phases by either voltage controlled devices or by altering the lengths of the feed lines), amplitude variations are also utilized via the use of variable gain amplifiers.
While there are some designs where the feed network has both phase and amplitude variations, the architectures that appear in the literature are only meant for a specific band of frequencies and cannot be used for others. In addition, most of them cover a limited number of frequency bands. For system level engineers, there is no generic architecture that they can use for rapid prototyping of their antenna array designs, where they do not need to worry about the feed network as an integral part of their antenna array design.
Thus, a programmable wide-band radio frequency feed network solving the aforementioned problems is desired.